Information coding, such as done to increase transmission robustness over wireless communication links, is commonplace. For example, U.S. App. No. 2002/0124224 A1 discloses the use of symbol repetition, where reception of the repeated symbols is improved by using maximal ratio combining of the repeated symbols. The ‘224 application further teaches that the number of symbols that are repeated can be adjusted to match the frame length of an encoder and/or a channel interleaver. As another example, the published international patent application WO 2006/011699 A1 discloses the use of bit repetition to increase robustness. The ‘699 publication particularly teaches a form of unequal error protection where the repetition count for particular bits in a set of bits to be transmitted is set according to their importance. For example, the MSB in binary word used to report signal quality is repeated more than the LSB in that word, given its relatively greater importance in terms of binary weight.
Other examples exist in, various wireless communication standards, for coding feedback information transmitted by a given first transceiver to a given second transceiver, for use by the second transceiver in adjusting one or more aspects of its transmissions to the first transceiver. As a particular example, Release 7 of the Wideband Code Division Multiple Access (WCDMA) standards define feedback information in support of MIMO operation to include channel quality indicators (CQIs), which may comprise CQI bits indicating channel quality at the receiver.
More particularly, for “Type-A” operations, Release 7 defines coded feedback based on the use of a “20, 10” code, where ten information bits represent an information word to be coded into a code word that is twenty bits long. Here, Type-A denotes the Multiple-Input-Multiple-Output (MIMO) operating mode, and particularly connotes a “2×2” case, where two information streams are concurrently transmitted from two antennas according to defined pre-coding weights. A corresponding MIMO transceiver provides feedback comprising eight CQI bits and two “PCI” bits, which comprise preceding indicator bits. This combination produces ten information bits, which matche the chosen “20, 10” code.
Problematically, however, the amount of CQI information is reduced for “Type-B” MIMO operations, which involve the transmission of one rather than two information streams. Correspondingly, the number of information bits, including CQI and PCI bits, needed to be fed back in each reporting period during Type-B operation is less than ten. Thus, a shortfall exists between the number of information bits to be encoded and the information word length requirements of the chosen code. More details for these various MIMO-related feedback operations are given in “FEC Coding of type-B CQI/PCI Information”, as presented by INTERDIGITAL at the 3GPP TSG RAN WG1 Meeting #47, on 15-16 Jan. 2007, in Sorrento, Italy (identified as Contribution R1-070493); further, one may refer to Contribution R1-070529, as presented by QUALCOMM in the same meeting. This latter presentation was entitled “Coding of HS-DPCCH to support operation of FDD MIMO”.
Such information bit shortfalls may arise in other coding applications as well, with similar challenges arising if it is desired to use the same code where the number of information bits input for coding is subject to variation.